In the following description reference will be made to a lens, especially to an automatically darkening lens that is able to operate automatically to control transmission of light. The lens may be a light shutter type of a device that is able to control light transmission without distorting, or at least with relatively minimal distortion, of the light and the image characteristics carried by the light or represented by the light. Therefore, when a person looks through the lens, the image seen would be substantially the same as the image seen without the lens, except that the intensity of the light transmitted through the lens may be altered depending on the operative state of the lens. The lens may be used in a welding helmet, and the lens may be used in other types of devices, such as goggles, face masks, other types of helmets, etc. Such devices usually are employed to protect the face or the eyes of a person, as is known, for example, in the field of welding and in other fields, too.
For the purposes of providing eye protection, usually a welding lens provides light blocking characteristics in the visible, infrared and ultraviolet wavelength ranges. The actual ranges may be determined by the components of the lens, the arrangement of those components, and so forth. One example of a lens useful in accordance with the present invention is disclosed in copending, commonly owned U.S. patent application Ser. No. 08/105,734, filed Aug. 11, 1993, the entire disclosure of which hereby is incorporated by reference. The lens assembly disclosed in that patent application includes several liquid crystal cell light shutters, several plane polarizers, and a reflector or band pass filter, which is able to reflect ultraviolet and infrared electromagnetic energy and possibly also some electromagnetic energy in the visible wavelength range. The several liquid crystal cells, for example, may be birefringent liquid crystal cells sometimes referred to as surface mode liquid crystal cells or pi-cells.
Examples of liquid crystal cells, lenses using them and drive circuits are described in U.S. Pat. Nos. 5,208,688, 5,252,817, 5,248,880, 5,347,383, and 5,074,647 and in pending U.S. patent application Ser. No. 08/027,385 filed Feb. 17, 1993. In U.S. Pat. No. 5,074,647, several different types of variable polarizer liquid crystal devices are disclosed. Twisted nematic liquid crystal cells used in an automatic shutter for welding helmets are disclosed in U.S. Pat. Nos. 4,039,254 and Re. 29,684. Exemplary birefringent liquid crystal cells useful as light shutters in the present invention are disclosed in U.S. Pat. Nos. 4,385,806, 4,436,376, 4,540,243, 4,582,396, and Re. 32,521 and exemplary twisted nematic liquid crystal cells and displays are disclosed in U.S. Pat. Nos. 3,731,986 and 3,881,809. The entire disclosures of the patents and applications mentioned herein are incorporated by reference.
As is disclosed in several of the above patents, the respective shutters may have one or more operational characteristics (sometimes referred to as modes or states). One example of such an operational characteristic is the shade number; this is the darkness level or value of the shutter when it is in the light blocking mode. Another exemplary operational characteristic is the delay time during which the shutter remains in a dark state after a condition calling for the dark state, such as detection of the bright light occurring during welding, has ceased or detection thereof has terminated or been interrupted. Still another operational characteristic is sensitivity of the detection circuit and/or shutter to incident light, for example, to distinguish between ambient conditions and the bright light condition occurring during a welding operation. Even another characteristic, which may be considered an operational characteristic, is the condition of the battery or other power source for the shutter, such as the amount of power remaining, operational time remaining until the power source becomes ineffective, etc. In the past various of the operational characteristics of such shutters have been adjustable or fixed. However, relatively large devices were used to adjust and to display the values or settings of such operational characteristics, as by dials or knobs. It would be desirable to reduce the space required for such components and to improve the operability of them. It would be desirable to minimize the size and weight of such control and display components thereby to minimize size and weight of a welding lens or other automatic shutter device. Further, it would be desirable to facilitate manufacturing such automatic shutters.
An example of a "welding lens with integrated display and method" is disclosed in copending, commonly owned U.S. patent application Serial. No. (Express Mail No. EM402013379US), filed Mar. 15, 1996. In the invention disclosed therein the current operational characteristics of the shutter can be displayed and can be selectively changed by operating one or more switches. The switches may be flexible membrane switches, microswitches, or another type of switch. It is desirable to reduce the size of the switches, space required in the shutter assembly for the switches and weight of the shutter assembly.
A cover lens, sometimes referred to as a cover plate, is useful for protecting the light shutter, and especially the liquid crystal cell thereof, in addition to the eyes of the user. For example, the cover lens protects the light shutter from damage or dirt due to contact with fingers, etc. A cover lens may be included in the welding helmet lens aperture in front of and/or behind the light shutter. In the event the cover lens itself becomes damaged, scratched, dirty, etc., it usually may be replaced relatively easily.
The present invention is particularly useful for eye protection by an automatic darkening light shutter in a helmet or goggle assembly or in another device, if desired. The switching mechanism for powering the light shutter on and off and/or for selecting operational characteristics is an integral part of the light shutter and/or frame assembly or other component or portion thereof.
The light shutter of the present invention may be used in a variety of embodiments and applications. The shutter is adjustable to control light, i.e., to increase or to decrease the amount of the incident light which is transmitted through the shutter. When welding is not occurring, for example, the shutter in a welding helmet may be substantially optically clear or transmissive or at least minimizes its attenuation of light. When welding is occurring, the shutter may be dark or closed to reduce the amount of light transmitted therethrough in order to protect the eyes of the person performing the welding and maximize his or her viewing comfort. In both cases, though, the image characteristics of the light preferably remain intact. A photosensitive device may be used to sense the intensity of light impinging in the area of the shutter so as to provide an input to a drive circuit for the shutter in order to control opening and closing thereof.
An example of a "welding lens with integrated display and method" is disclosed in copending, commonly owned U.S. patent application Serial. No. (Express Mail No. EM402013379US), filed Mar. 15, 1996.
The disclosures of the patents and patent applications identified herein are specifically incorporated in their entirety by reference.